Preparation of acrylonitrile di-adducts of primary aliphatic amines



United States Patent 3,028,415 PREPARATION OF ACRYLONITRILE DI-ADDUCTS OF PRIMARY ALIPHATIC AMINES Robert Nordgren, Minneapolis, Minn., assignor to General Mills, Inc., a corporation of Delaware No Drawing. Filed May 1, 1959, Ser. No. 810,244 5 Claims. (Cl. 260-4655) The present invention relates to an improved process for the preparation of the di-adducts of acrylonitrile and primary aliphatic amines.

The di-adducts of acrylonitrile and primary aliphatic amines are valuable intermediates in the production of surface-active materials and may be represented by the formula RN(CH CH CN) inwhich R is an aliphatic hydrocarbon group containing from 8 to 22 carbon atoms.

It is well known that the primary aliphatic amines react readily with acrylonitrile to form the mono-adduct or N-alkyl beta amino propionitriles. The formation of the mono-adduct proceeds rapidly at temperatures over 70 C and in the presence of alcohol is essentially completed within 15 to 30 minutes. Under these same conditions, however, even when a large excess of acrylonitrile is present, the di-adduct is not formed to any great extent as less than 2% is usually formed.

The principal means of preparing the di-adducts of acrylonitrile and primary aliphatic amines in the past have been by methods which require the use'of acid catalysts, large excesses of acrylonitrile (2 to times the theoretical amount) and lengthy reaction times. Even when relatively strong acidic catalysts such as 2% acetic acid were used, the previously known procedures for the preparation of the di-adduct required that a large excess of acrylonitrile be used and that the reaction mixture be heated and maintained at 7090 C. for at least 16 hours in order to obtain a yield exceeding 80% of the di-adduct.

It is an object of the present invention to disclose a process by which the di-adducts of acrylonitrile and primary aliphatic amines may be prepared in high yields in relatively short reaction times.

It is a further object of the present invention to disclose a process by which the di-adducts of acrylonitrile and primary aliphatic amines may be prepared without employing a large excess of acrylonitrile.

I have now made the totally unexpected discovery that the rate at which the di-adduct formation reaction proceeds may be materially accelerated if the reaction is conducted in the presence of an added amount of water. In addition, I find that when the reaction is so conducted it is possible to obtain these high yields of the di-adduct although as little as 25% excess acrylonitrile is utilized. Still other advantages of my invention over the prior art will be readily apparent to those skilled in the art.

In the practice of the present invention, a mixture comprising the primary aliphatic amine, acrylonitrile, an acidic catalyst and an added amount of water is heated to and maintained at a temperature of approximately 60- 90 C. for 6 to 10 hours, at which time the reaction is usually essentially completed.

In general, the primary aliphatic amines, which are contemplated for use in the present invention, are those amines which contain from 8 to 22 carbon atoms.

Although single amines may be used in the invention with excellent results, the mixture of amines obtained by the amination of the fatty acids or selected fractions thereof present in any animal or vegetable fats or oils such as tallow, coconut oil and the like are well suited for use in the preparation of the di-adduct. One exarnple of such an amine is cocoamine which is derived from coconut oil and contains fatty groups of 8 to 18 carbon atoms, most of which are saturated, but some of which are unsaturated. Another such amine is tallow amine which is derived from tallow and contains fatty groups of K reaction to proceed most rapidly.

3,028,415 Patented Apr. 3, 1962- 14 to 18 carbon atoms, some of which are saturated and others of which are unsaturated.

The amount of acrylonitrile contemplated for use in the present invention is not critical. I prefer to use a slight excess of acrylonitrile but generally it is not necessary to exceed 2.5 equivalents per equivalent of primary fatty amine. Larger amounts can be used but the use of larger amounts makes it an economic necessity to recover the unreacted acrylonitrile because of the cost of this compound. Two to twenty equivalents of acrylonitrile may be employed for each equivalent of primary aliphatic amine.

In general, the relatively strong acids such as acetic acid and phosphoric acid are the most effective catalysts for the di-adduct formation reaction, as they cause the However, acetic acid when used as the sole catalyst causes an excessive darkening of the reaction product, and accordingly is not preferred where a light colored product is desired. On the other hand, phosphoric acid when used alone tends to cause foaming when the unreacted acrylonitrile is later stripped from the reaction mixture and so it is likewise not preferred when used alone.

I have found that the combination of 2% glacial acetic acid and 0.5% of 85% phosphoric acid as basedon the weight of the primary aliphatic amine is an excellent catalyst for the di-adduct formation reaction. When using this catalyst the di-adduct formation reaction proceeds very rapidly and a light colored, nonfoaming di-adduct is obtained.

The accelerating action of the water upon the di-adduct formation reaction appears to be in no way dependent upon the specific catalyst being employed in the reaction. For example, even in reactions in which the acetic acid or phosphoric acid is employed individually as the sole catalyst, it is found that the addition of water materially accelerates the formation reaction.

The amount of water to be added to the reaction mixture may be relatively small, much less than is usually considered a solvent quantity. I find it preferable to add 2-20% water as based on the weight of the primary aliphatic amine, in most instances. When the preferred catalyst, namely the combination of acetic and phosphoric acid, is used it is found that the addition of the water has the efiect of producing yields of the di-adduct up to and exceeding 20% higher than the corresponding yields obtainable when the same catalyst is used and water is not present.

While the presence of a lower aliphatic alcohol is not essential, I find it desirable and preferable on some occasions to have a small amount such as 320% as based on the weight of the primary aliphatic amine, of either methanol, ethanol, propanol, butanol or one of their isomers present in the reaction mixture as it appears to insure maximum yields of di-adduct.

While the di-adduct formation reaction can be conducted at temperatures ranging from 60-l00 C., I find it preferable to use the lower temperatures (approximately 70 C.) to obtain the lighter colored di-adducts.

The following examples further illustrate the practice of the present invention:

Example 1 One equivalent of commercial distilled dodecyl amine (194 g.), methanol (20 g.), 2.5 equivalents of acrylonitrile (132.5 g.) and acetic acid (4 g.) were stirred and heated under reflux at 70-75 C. for 7 hours. The excess acrylonitrile, methanol and possibly some acetic acid were removed by heating the reaction product up to C. under a vacuum of 25 mm. The yield was 283 g., and the solution had a 41.5% transmission when measured at 450 mu. with a Coleman Junior Spectrophotometer.

As the di-adduct is the only tertiary amine present in the reaction mixture, the percent of di-adduct present was determined by direct titration of the tertiary nitrogen atom. The tertiary nitrogen content was 54%.

Example ll One equivalent of commercial distilled dodecyl amine (194 g.), methanol (20 g.), 2.5 equivalents of acrylonitrile (132.5 g.), acetic acid (4 g.) and 85% phosphoric acid (1 g.) were stirred and heated at 70-75 C. for 7 hours, after which the excess acrylonitrile and methanol were stripped off as in Example I. The yield was 291 g., the tertiary amine content was 62% and the solution had a percent transmission of 60.0 at 45 mu.

Example III Example IV One equivalent of commercial distilled dodecyl amine (194 g.), water (20 g.), 2.5 equivalents of acrylonitrile (132.5 g.), acetic acid (4 g.) and 85% phosphoric acid (1 g.) were stirred and heated at 70-75 C. for 7 hours, after which the excess acrylonitrile and water were stripped off as in Example I. The yield was 302 g., the tertiary amine content was 82.0% and the solution had a percent transmission of 77.0 at 450 mu.

Example V One equivalent of tallow amine (131.5 g.), methanol (6.5 g.), water (13 g.), 2.5 eq. of acrylonitrile (66.2 g.), glacial acetic acid (2.63 g.) and 85% phosphoric acid (0.65 g.) were stirred and heated under reflux at 76 C. for 7 hours. The reactants were stripped as usual. The yield was 185 g. and the tertiary amine content was 90.5%.

It is to be understood that the present invention is to cover all changes and modifications of the invention which do not constitute departure from the spirit and scope of the invention.

I claim as my invention:

1. The method of preparing fl,B'-fatty imino-dipropionitriles which comprises reacting a primary fatty amine having 8 to 22 carbon atoms in the fatty radical with an excess of acrylonitrile at a temperature of 60-100 C. in the presence of an acid catalyst and an added amount of water equal to 2-20% by weight of the amine.

2. The method of claim 1, where the acid catalyst is a combination of 2% glacial acetic acid and 0.5% of phosphoric acid based on the weight of the primary amine present.

3. The method of claim 1, where the primary fatty amine is tallow amine.

4. The method of claim 1, where the primary fatty amine is dodecyl amine.

5. The method of preparing i -fatty imino-dipropionitriles which comprises reacting a primary fatty amine having 8 to 22 carbon atoms in the fatty radical with an excess of acrylonitrile at a temperature of 60-100 C. in the presence of an acid catalyst, a lower aliphatic alcohol containing 1 to 4 carbon atoms, and an amount of water equal to 2-20% by weight of the amine.

References Cited in the file of this patent UNITED STATES PATENTS 1,992,615 Hotr'mann et al. Feb. 26, 1935 2,768,962 Krimm Oct. 30, 1956 2,787,633 Harrison et al. Apr. 2, 1957 

1. THE METHOD OF PREPARING B,B''-FATTY IMINO-DIPROPIONTRILES WHICH COMPRISES REACTING A PRIMARY FATTY AMINE HAVING 8 TO 22 CARBON ATOMS IN THE FATTY RADICALS WITH AN EXCESS OF ACRYLONTRILE AT A TEMPERATURE OF 60-100*C. IN THE PRESENCE OF AN ACID CATALYST AND AN ADDED AMOUNT OF WATER EQUAL TO 2-20% BY WEIGHT OF THE AMINE. 